Plastic boat construction

ABSTRACT

Boats constructed of reinforced plastic which are self-buoyant. Fiberglass boats (e.g., runabouts) which will float in an upright position when filled with water have their hulls constructed in part-at-least as foamed-core sandwich panels or laminates. They are characterized by the absence of flotation chambers in the bilge area below the floor and by the presence of more foamed plastic in the laminates above the waterline than below the waterline.

United States Patent [4 1 Jan. 18,1972

Geiger [54] PLASTIC BOAT CONSTRUCTION [72] Inventor: Earl E. Geiger, Edina, Minn.

[73] Assignee: Larson Industries, Inc., Edina, Minn.

[22] Filed: Apr. 23, 1970 [21] Appl. N0.: 31,265

[52] U.S. Cl ..9/6 [51 Int. Cl L ..B63b 5/24 [58] Field oiSearch ..9/3, 6, 6.5; 114/69, 68

[56] References Cited UNITED STATES PATENTS 3,383,720 5/1968 Greig et a1. .f. ..9/6 3,531,809 10/1970 Hegg ..9/6

2,381,631 8/1945 Waxing ..9/6

Primary Examiner-Milton Buchler Assistant ExaminerCa.rl A. Rutledge Attorney-Merchant & Gould [5 7] ABSTRACT 7 Claims, 4 Drawing Figures PATENIED .mu 8 I972 INVENTOR. EARL B. 65/65,?

BY M

AT TORN E VS PLASTIC BOAT CONSTRUCTION IMPROVED PLASTIC BOAT CONSTRUCTION CROSS-REFERENCE TO RELATED APPLICATION Ser. No. 766,868, filed Oct. ll, 1968, by Allan B. Hegg which describes self-buoyant boats constructed as foamedcore sandwich panels or laminates.

BACKGROUND OF THE INVENTION Boats, particularly pleasure boats, are being made in increasing numbers from reinforced plastics such as glass-reinforced polyester resins. Among the numerous advantages of such boats are their ease of maintenance and repair.

Many boats constructed of reinforced plastic are selfbuoyant when empty but do not have sufficient buoyancy to support the fumaric weight of maleic usually carried by such boats (e.g., outboard motors, fuel, fishing and hunting gear, etc.). Consequently, it is common practice to equip boats constructed of reinforced plastic with flotation tanks (e.g., paired longitudinal flotation tanks in the bilge) to provide added buoyancy. However, such boats characteristically overturn (i.e., float bottom side Reinforcing Materials filled with water, particularly if they are unevenly loaded or are rocked from side to side. Even if turned upright (e.g., as by a swimmer) such boats frequently exhibit a marked tendency to roll over" again. This is disadvantageous from the standpoint of human safety and because it causes loose equipment (e.g., fishing tackle) to be lost form the boat. 7

More recently, self-buoyant plastic boats have been developed which are characterized by having their hulls constructed as foam-core sandwich panels and which are further characterized by a stabilizing wet bilge located between paired longitudinal flotation tanks located in the bilge. Such boats represent a substantial advance in the plastic boat industry and are more fully described in the patent application previously identified herein.

SUMMARY OF THE INVENTION The present invention is an improvement in self-buoyant plastic boats of sandwich foam construction.

Plastic boats constructed according to this invention are self-buoyant and will generally remain upright when filled with water (i.e., swamped), even when loaded to their B.I.A. capacity.

Boats constructed according to this invention are characterized by having their hulls constructed as sandwich panels or laminates comprising a core of foamed plastic (e.g., polyurethane foam) sandwiched between or surrounded by a plastic skin or shell (e. g., a glass-reinforced polyester shell). The bulk volume of foamed plastic above the waterline is greater than the volume of foamed plastic below the waterline.

Another feature of boats constructed according to this invention is the absence of flotation chambers below the floor (i.e., in the bilge) which thereby increases the effective size of the wet bilge.

Among the several advantages of the present invention are sufficient buoyancy in the boats of this construction to support or float the boat and its usual added gear (e.g., an inboard/outboard motor and gasoline tank) in an upright position when filled with water. Other advantages include improved quietness of operation (i.e., a noticeable reduction of the typical sounds common to reinforced plastic boats of conventional design) and increased strength. Elimination of the bilge flotation tanks or chambers permits better use of space and materials as well as improving the stability of upright flotation.

THE DRAWINGS FIG. I is a perspective view of an outboard runabout having a forward deck and a dihedral bottom of clinker design.

FIG. 2 is a fragmentary sectional view illustrating the foamed-core laminate construction used for the hull.

FIG. 3 is a cross-sectional view of the boat shown in FIG. I as taken along lines 33 in the direction of the arrows.

FIG. 4 is a cross-sectional view illustrating a variation in construction from that shown in FIG. 3.

DETAILED DESCRIPTION The present invention is directed to boats of improved construction which are strong, quiet and self-buoyant. Boats made according to the preferred form of the present invention will float stably in an upright position when filled with water, even when heavily loaded.

The present invention is hereinafter described with reference to the drawings. For purposes of convenience and without intending to be limited thereby, the invention is described with particular reference to an outboard runabout of particular design, it being understood that other types and designs of the plastic boats can be made according to the teachings of this invention. The invention is particularly applicable to pleasure boats having an overall length of less than 10 meters (e.g., less than 7 meters).

The Boats FIG. I is a perspective view of an outboard runabout constructed of reinforced plastic. The boat comprises a hull (generally designated by the numeral 1) and a forward deck 2 carried by hull I. For ease of construction and added strength, deck 2 is integrally formed with side rails 3 and 4 and motor well 5. Hull 1 is comprised of sidewalls 6 and 7, a transom 8 and a dihedral bottom 9. As shown in FIG. 1, bottom 9 is of clinker design. The midsection of hull l is the vertical plane which passes through keel 10 (i.e., the plane of symmetry).

According to this invention, hull l is constructed in part-atleast as a foamed-core sandwich panel or laminate comprising a core of foamed plastic sandwiched between or surrounded by plastic skins or shells. Optionally, the deck 2 can also be constructed as a foamed-core sandwich panel.

Sandwich panels of this type can be prepared by a filling process which comprises, for example, forming two nestable hull-shaped shells or skins of reinforced plastic on two separate molds, placing the smaller of the two reinforced plastic shells inside the larger shell, holding the two shells in a spaced relationship (e.g., separated by 2-10 cm.) and then blowing a foam-producing agent between the two shells. On hardening, the foam-producing agent will form a rigid or flexible cellular plastic core between the two shells. The cellular core can have open or closed cells. Any exposed edges of the core can be sealed or enclosed by using additional plastic of the type used to form the hard shells (e.g., reinforced polyester).

However, the use of two separate molds for forming the inner and outer skins or shells of sandwich panels, particularly in the manufacture of boats, is generally uneconomical. Consequently, sandwich panels of this type are preferably prepared by a process of superposition (i.e., the orderly fabrication of layers). According to this process, a reinforced plastic outer skin or shell is fonned in a conventional female hull mold. Subsequently, one or more layers of plastic foam are formed in place on the inside of this outer skin or shell. Finally, an inner reinforced plastic skin or shell is formed in place over the last applied layer of foam.

The sandwich panels which result from these various processes are illustrated in FIG. 2. The outer skin or shell can consist of a polyester gel coat ll backed with one or more layers or reinforced polyester 12 (c.g., polyester reinforced with glass fibers). The inner shell can consist of one or more layers of reinforced polyester 13. Sandwiched between and bonded to the outer and inner shells is a foamed plastic core 14 (e.g., rigid polyurethane foam).

A feature of the present invention is the elimination of flotation chambers from the bilge (i.e., from below floor 20 as shown in FIG. 3). If desired, under seat flotation (as contrasted to under floor or bilge flotation), may be used.

It is essential in the practice of this invention that a substantial volume of foamed plastic be used above the waterline of the boat. Although some foam may be used below the waterline (e.g., all or part of bottom 9 can be constructed as a foamed-core laminate), the bulk volume of foam above the waterline must be greater than the volume of foam below the waterline. This ratio can be expressed mathematically as:

This ratio has been arbitrarily called the buoyancy factor. If a constant bulk density foam is used, the buoyancy factor can also be determined by dividing the weight of foam above the waterline by the weight of foam below the waterline. In boats constructed according to this invention, the buoyancy factor will always be greater than 1, desirably at least 1.5, and preferably at least 3. High buoyancy factors are desirable.

According to this invention, the primary purposes of using foam below the waterline are for quietness and structural strength, not for buoyancy. Rather, buoyancy and stability when swamped are obtained in the present invention by placing foam above the waterline and outboard of the midsection of the hull I. In general, it has been found that stability when swamped increases as the foam flotation is moved higher above the waterline and further away from the midsection of the hull 1. Of course, distribution of the foam should be generally unifonn about the plane of symmetry to avoid imbalance and should also meet the need for buoyancy when the boat is filled to its maximum safe capacity (e.g., its B.I.A. capacity).

As used herein, waterline" means the waterline of the unloaded or empty boat when resting in calm water (contra various loadlines and the Plimsoll line). However, most plastic pleasure boats have such a wide beam and a shallow draft that there is little difference (e.g., 5 cm. difference) between the waterline and the loadline corresponding to the manufacturers maximum recommended safe load.

It is not necessary that entire sides 6 and 7 be constructed as foam-core laminates. However, it is convenient and preferred to do so. In any event, it is preferred to use a substantial volume of foam along sides 6 and 7 at or near the gunwales to thereby provide a large ring of buoyant material around the boat.

Two alternative forms of hull construction are shown in FIGS. 3 and 4.

FIG. 3 is a crosssectional view of the boat of FIG. 1 as taken along the line 3-3 in the direction of the arrows. As shown in FIG. 3, the sidewalls 6 and 7 and bottom 9, which together form the outer shell or skin of hull l, are covered with a layer of foamed plastic 15 (e.g., polyurethane foam) which is relatively thin in the bilge area (e.g., 1-2 cm. thick) and substantially thicker along sidewalls 6 and 7 (e.g., 10 or more cm. thick). Note that most of the foam (volumewise) is positioned high along sidewalls 6 and 7 near gunwales 3 and 4. The waterline is indicated at 16. The inner shell of the boat 17 is of reinforced plastic (e.g., reinforced polyester) which is formed in place over the foamed plastic 15. A floor 20 is positioned in the hull 1 below the waterline 16.

FIG. 4 is a cross-sectional view of an alternative hull design. In FIG. 4, the sidewalls 6 and 7 are covered with a layer of foam of varying thickness. The waterline is again noted at 16'. The foam 15 is again concentrated along the sidewalls 6 and 7 especially near gunwales 3 and 4. Panels 18 and 19 can be attached to inner shell 17 as shown to fonn sidewall storage compartments in the boat. Note that when the foam is concentrated near the gunwales 3' and 4 and carried all or most of the way around the boat, the effect is to surround any occupants of the boat with a buoyant ring much like a life buoy. A floor 21 is supported by stringers 22 and 23. If desired, such stringers can be made as foam core laminates but the amount of foam contained therein will be so small as to be negligible. Such stringers do not function as flotation chambers.

Note that in FIGS. 3 and 4 there are no flotation chambers in the bilge. Their absence reduces the tendency for these boats to roll over when swamped, particularly when large amounts of foam are used high along the sidewalls.

In both of the embodiments as shown in FIGS. 3 and 4, any decks or other structures can be made as sandwich foam panels to provide added buoyancy, strength and quietness.

Plastics for the Shells or Skins Suitable plastics are known in the art. Although all plastics do not serve with equal effectiveness, their selection is within the skill of the art. Among the many plastics are ABS resins (i.e.; acrylonitrile-butadiene-styrene resins) and unsaturated polyester resins. Unsaturated polyester resins are in widespread use in the manufacture of boats and are preferred because of their good qualities, low cost, and ease of application.

The commercially important polyester molding resins are the polycondensation products of dicarboxylic acids and dihydric alcohols. Occasionally, these polyester resins are chemically modified with minor amounts of mono and polyfunctional materials (e.g., i-stearic acid and pentaerythritol). The polyesters commonly used in the manufacture of boats are unsaturated polyesters characteristically containing ethylenic unsaturation (Le. the structuro C=C Ethylenic unsaturation can be and frequently is introduced into polyester resin molecules by the use of maleic or fumaric acid or maleic anhydride in the manufacture of the resin. Unsaturated polyester resins can be cross-linked and hardened through the double bond of the ethylenic unsaturation using compatible monomers which also contain ethylenic unsaturation (e.g., styrene). Polyester resins, when catalyzed (e.g., catalyzed with benzoyl peroxide) will cure or harden at room temperature.

Reinforcing Materials Although a variety of reinforcing materials are known in the art, (e.g., paper, nylon, metal filaments, etc.) glass fibers are the most common. The selection of suitable reinforcing materials (e.g., chopped glass fibers, woven fabrics, etc.) is within the skill of the art.

Foam Producing Agents Suitable foam producing agents are those which produce open or closed cell plastic foams such as those which produce polyurethane, polyester and polystyrene foams. Such agents are known in the art. Polyurethane foams are preferred. As is known in the art, polyester foams are a particular species of polyurethane foams and are produced by the reaction between polyesters of relatively high acid or hydroxyl numbers with dior poly-isocyanate cross-linking agents such as hexamethylenediisocyanate and toluene diisocyanate, aided by suitable flowing agents.

Because the cellular plastic foams used in this invention are preferably completely encapsulated or enclosed between nonporous shells or skins (e.g., glass-reinforced polyester skins) either open or closed cell foams can be used. However, closed cell foams are preferred because of the added safety factory which they provide in circumstances under which the surrounding skin or shell is or may be punctured or ruptured.

Construction of a Boat The construction of a typical boat of this type is hereinafter described with reference to FIGS. 1-3.

The outer shell of the hull can be prepared in a seamless hull mold as follows. First, a l5-mil polyester gel coat is applied over the inner'hull-defining surface of the mold. Next, a 45- mil layer of polyester resin reinforced with continuous, nonoriented glass fibers is applied over the gel coat. Next, a woven fiberglass matt, saturated with polyester resin, is ap plied over the previous layer of reinforced polyester.

Meanwhile, a deck and transom assembly 2-5 is prepared as shown in FIG. l. The outer shell 27 of this assembly is prepared in a female mold by the sequential application of a lS-mil polyester gel coat, a l0-mil layer of polyester reinforced with glass cloth, and a 45-mil layer of polyester reinforced with chopped glass fibers.

Next, the interior or underside of the front deck portion of the outer shell 27 of the deck and transom assembly 2-5 is coated with two layers (each 1-2 cm. thick) of polyurethane foam by spray application. The underside of the rear deck (i.e., the motor well or splash well as it is sometimes called) is also coated with a single 1-2 cm. layer of polyurethane foam by spray application. Finally, the polyurethane foam coatings on the front and rear decks are covered with a 45-mil layer of polyester resin reinforced with chopped glass fibers. Adhesion of this inner polyester skin is enhanced if the polyurethane foam is first coated with a thin primer coating of polyester resin within l-60 seconds (e.g., within -50 seconds) after the polyurethane foam-producing agent has been applied to the deck and transom assembly and before the foam has hardened (i.e., while it still foaming).

Deck assembly 2-5 is bonded to hull 1 by the use of a glass reinforced polyester adhesive. Preferably, this is accomplished after the sidewalls have been sprayed with foam l5 and polyester 17 as hereinafter described.

Then, the interior of sidewalls 6 and 7 and bottom 9 of hull l are sprayed with several layers of a foam-producing agent to produce a polyurethane foam blanket or core as shown in FIG. 3. Then, foam-core 15 is covered with an inner shell R7 of glass-reinforced polyester (about 45 mils thick). The amount of foam is such that the buoyancy factor is greater than 3.

The resulting boat can then be completed in a conventional manner by, for example, the installation of a floor, a windshield, running lights, and a steering wheel.

The amount of foam used in manufacturing such a boat should be sufficient to provide a total buoyancy substantially in excess of that required to float the boat when loaded to its B.l.A. (Boating industries Association) capacity.

In addition to providing the potentially lifesaving safety feature of upright flotation when swamped, boats of this construction are stronger than comparable boats of conventional design and are quieter in operation (i.e., engine noises and vibrations from wave pounding are dampened).

What is claimed is:

1. Boats which comprise:

a. a hull having an outer plastic shell which forms the sidewalls and bottom of said hull;

b. said hull being free of flotation chambers below the floor;

c. said sidewalls being constructed generally as foamed-core laminates or sandwich panels having inner and outer shells and a core of foamed plastic sandwiched between said inner and outer shells; and

d. the bulk volume of said foamed plastic is greater above the waterline than the bulk volume of said foamed plastic below the waterline.

2. Boats of claim 1 wherein said foamed plastic is polyurethane foam.

3. Boats of claim 2 wherein said plastic shell comprises glass-reinforced polyester.

4!. Boats of claim 3 wherein said boats are runabouts having an overall length of less than 7 meters and a buoyancy factor ofat least 1.5.

5. Boats of claim 4 wherein said runabouts are inboard/outboard runabouts having a forward deck carried above the waterline by said sidewalls, which deck is also constructed as a foamed-core laminate or sandwich panel.

6. Boats of claim 3 wherein the bottom of said hull is also constructed as a foamedcore laminate or sandwich anel.

7. Boats of claim 3 wherein the bottom of said ull 15 not constructed as a foamed-core laminate or sandwich panel.

UNITED STATESigPATENT OFFICE CERTIFICATE OF CORRECTEUN Patent No. 3: 3 H 9 I Dated January 18, 1972 Inventor(s) Earl E. Geiger It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown-below:

Column 1, line 18, "fumaric weight ofmaleic" should read added weight of equipment line 24, "Reinforcing Materials" should read up) when line 30, "form" should read from Column 4, line 61, "flowing" should read blowing line 74, "seamless" should read female I Signed and sealed this 7th day of November 1972.

(SEAL) Atteet:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-105O (10-69) USCOMM-DC BOS75-P6Q i 11.5. GOVERNMENT FRlNTlNG OFFICE (9H9 0-856-334, 

1. Boats which comprise: a. a hull having an outer plastic shell which forms the sidewalls and bottom of said hull; b. said hull being free of flotation chambers below the floor; c. said sidewalls being constructed generally as foamed-core laminates or sandwich panels having inner and outer shells and a core of foamed plastic sandwiched between said inner and outer shells; and d. the bulk volume of said foamed plastic is greater above the waterline than the bulk volume of said foamed plastic below the waterline.
 2. Boats of claim 1 wherein said foamed plastic is polyurethane foam.
 3. Boats of claim 2 wherein said plastic shell comprises glass-reinforced polyester.
 4. Boats of claim 3 wherein said boats are runabouts having an overall length of less than 7 meters and a buoyancy factor of at leAst 1.5.
 5. Boats of claim 4 wherein said runabouts are inboard/outboard runabouts having a forward deck carried above the waterline by said sidewalls, which deck is also constructed as a foamed-core laminate or sandwich panel.
 6. Boats of claim 3 wherein the bottom of said hull is also constructed as a foamed-core laminate or sandwich panel.
 7. Boats of claim 3 wherein the bottom of said hull is not constructed as a foamed-core laminate or sandwich panel. 